Effect of luting agent on the bond strength of ceramic-based lithium disilicate and titanium abutment subjected to artificial aging

This study aimed to evaluate the bond strength (BS) of a ceramic coping-abutment implant interface according to the luting agent, before and after thermal cycling (TC). Methodology: Forty ceramic copings and abutments (Ti) were divided into four groups (n=10): OZ (zinc oxide eugenol free), PZ (zinc phosphate), GIC (resin modified glass ionomer), and RC (adhesive resin cement). BS test was performed using a universal testing machine before and after TC. Analysis of variance (ANOVA) and Tukey test (p<0.05) were performed for the means. Results: The results showed that before TC, the values ranged from 50.77 N (OZ) to 240.21 N (GIC). After TC, the values showed intermediate results - 3.5 N (OZ) and 330.66 N (RC), 90.58 N (PZ), and 280.43 N (GIC). OZ performed the worst, both before and after TC. Before TC, GIC had the highest value. After TC, RC had the highest value of BS. Conclusions: The aging process influenced and inverted the results of the GIC and RC groups, and had a greater negative impact on the OZ group

The effect of endodontic instrumentation on fatigue, fracture load, and dentin crack formation in restored uniradicular teeth: in vitro study

Objective(s): The aim of this study was to evaluate the effect of manual, rotatory, and reciprocating endodontic instrumentation for uniradicular teeth on fatigue, load to failure, and dentin crack formation. Materials and Methods: Sixty-two human uniradicular teeth were selected. Root samples were standsdized at 14 mm (t0). Teeth were divided into three groups according to endodontic instrumentation: Manual (M), Rotatory (RT), or Reciprocating (RC) and filled with passive technique (t1). All teeth received the cementation of a glass fiber post and were restored with composite resin core (t2) and metallic crown. Samples were subjected to mechanical cycling (177 N, 2x106 cycles, 4 Hz) (t3), followed by a load to failure test. Failure analysis was performed and dentin crack analysis was conducted in two samples each time t0, t1, t2, and t3. Results: Load to failure was not different between groups (p=0.716). However, the M group presented more irreparable failures. M and RC groups presented a high percentage of root sections with defects, and t3 was the evaluation time which presented more dentin crack formation. Conclusion(s): Endodontic instrumentation system did not affect load to failure of uniradicular teeth. Still, it affected the failure mode, with manual and reciprocating instrumentations presenting more irreparable failures and high root dentin crack formation

Dimensional change of impression materials for dental prothesis using different measuring methods

The aim of this study was to verify the effectiveness of alternative techniques for measuring the linear dimensional change of molds obtained by different impression materials. A stainless-steel die containing three lines was used to get the impressions. The impression materials were handled according to the manufacturers' instructions. After gelation/polymerization time, the molds (n=12) were stored for 30 minutes and the lines were subsequently measured using: a microscope (Olympus Measuring Microscope STM; Olympus Optical Co) with a 30x magnification (MM, control group), a digital caliper (Mitutoyo Digimatic; Kawasaki) (DC) and digitization using a digital camera (Canon EOS Rebel 3Ti; Canon)  (DI). For each mold, a mean of the length of the lines was obtained. For each impression material, the difference in the length between the metallic matrix and the mold was considered as linear dimensional change (%). The data were submitted to the non-parametric Kolmogorov-Smirnov test, followed by one-way Analysis of Variance (ANOVA) for each material, and the means were compared by the Tukey test (α=0.05). The DI group promoted values of dimensional accuracy without significant differences with the control group (MM), except for the putty-body condensation silicone. The DC group showed significant differences for MM and DI groups for all impression materials tested. The DI group showed to be a reliable methodology (Standard error of the mean 10%) to measure the linear dimensional change of all impression materials. The DI group presented molds with linear dimensional change values without significant differences with MM group, except for the putty-body addition silicone. The digitization is a reliable methodology to evaluate the linear dimensional changes of molds made with impression materials, except for the putty-body elastomeric impression materials.Key words: Dimensional Measurement Accuracy; Dental impression materials; Microscopy

Influência de diferentes aplicações de cargas e interposição de aparelho oclusal plano em implantes dentais: análise fotoelástica

Introdução: Se forças oclusais excederem a capacidade de absorção do sistema implante/osso, o implante tende a fracassar. O objetivo deste estudo foi avaliar a tensão peri-implantar com e sem utilização de placa oclusal plana sob carregamentos diferentes. Materiais e Métodos: Foram confeccionados cinco modelos fotoelásticos, com um implante em cada. Sobre estes implantes foram instaladas coroas unitárias e construída uma placa oclusal plana. Foram aplicadas cargas axiais de 100N, 200N e 300N, com e sem a presença da placa oclusal plana, por meio da máquina universal de ensaio conjugada ao polariscópio. O teste de Mann-Whitney foi utilizado para comparar os grupos com e sem placa, em todas as condições de carregamento. O teste de Kruskal-Wallis foi utilizado para comparar as tensões decorrentes das cargas de 100, 200 e 300N e também para comparar as tensões nas seis áreas periimplantares analisadas. Resultados: Os resultados dos testes de Mann-Whitney não identificaram diferenças estatísticas (p0,05) ao comparar as ordens de franjas com e sem a utilização de aparelho oclusal plano, em todas as áreas periimplantares analisadas, sob cargas verticais de 100, 200 e 300N. Os resultados dos testes de Kruskal-Wallis indicaram tensões significativamente maiores nas regiões apicais (pConclusões: A utilização da placa oclusal plana sobre a prótese unitária não reduziu significativamente as tensões nas regiões periimplantares; as tensões tendem a se concentrarem na região periapical e nestas áreas a maior magnitude de força implicou em maior tensão.

Influence of disinfection with peracetic acid and hypochlorite in dimensional alterations of casts obtained from addition silicone and polyether impressions

Made available in DSpace on 2019-09-12T16:26:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2013Dental impressions disinfection is important to reduce the risk of cross contamination but this process may produce dimensional distortions. Peracetic acid is a disinfectant agent with several favorable characteristics yet underutilized in Dentistry. The aim of this paper is to compare the dimensional stability of casts obtained from addition silicone and polyether impressions that were immersed for 10 minutes in a solution of 0.2% peracetic acid or 1% sodium hypochlorite. Sixty samples in type IV gypsum were produced after a master cast that simulated a full crown preparation of a maxillary premolar. Samples were divided in 6 groups (n = 10) according to the impression material and disinfection agent: Group AC - addition silicone control (without disinfectant); Group APA - addition silicone + 0.2% peracetic acid; Group AH - addition silicone + 1% sodium hypochlorite; Group PC - polyether control (without disinfectant); Group PPA - polyether + 0.2% peracetic acid; Group PH - polyether + 1% sodium hypochlorite. Cast height, base and top diameter were measured and a mean value was obtained for each sample and group all data was statistically analyzed (ANOVA, p < 0.05). There was not a significant statistical difference between addition silicone and polyether impressions regardless of the disinfectant materials. It can be concluded that disinfection with the proposed agents did not produce significant alterations of the impressions and the peracetic acid could be considered a reliable material to disinfect dental molds.Queiroz, D.A., Department of Dentistry, University of Vila Velha, Vila Velha, Espírito Santo, BrazilPeçanha, M.M., Department of Prosthodontics, University Federal of Espirito Santo Vitória, Espírito Santo, BrazilNeves, A.C.C., Department of Prosthodontics, University of Taubaté Taubaté, São Paulo, BrazilFrizzera, F., College of Dentistry at FAESA, Vitória, BrazilTonetto, M.R., Faculty of Dentistry, University of Cuiabá, Cuiabá, Brazilda Silva-Concílio, L.R., Department of Prosthesis, University of Taubaté, Taubaté São Paulo, Brazi

Evaluation of Castable and Premachined Metal Base Abutment/Implant Interfaces Before and After Cyclical Load

Made available in DSpace on 2019-09-12T16:53:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2014Purpose:The purpose of this study was to compare the vertical fit of the castable abutment/implant and premachined base metal abutment/implant interface, before and after cyclic loading.Materials and Methods:Ten UCLA abutments were distributed in 2 groups: castable and premachined with a cobalt-chromium metal base. The abutments were cast in cobalt-chromium alloy and were screwed onto implants (3.75 x 13 mm, external hexagon) with a 32 Ncm torque. The vertical gap (in micrometers) at the interface abutment/implant was evaluated by linear microscope 2 times: after torque and after cyclic load (1 million cycles, 400 N).Results:The mean values of the vertical gap at the castable abutment/implant and premachined abutment/implant interfaces before and after cyclic load were 5.33 to 6.64 mu m and 7.36 to 8.16 mu m, respectively. The mean values of the vertical gap were statistically analyzed (ANOVA and t test, P 0.05). Vertical gap values of the castable abutment/implant interface were not significantly different from those of the premachined abutment/implant interface, before (P = 0.154) and after (P = 0.471) cyclical loading.Conclusion:Castable and premachined base metal abutments showed similar gaps at the implant/abutment interface, both after applying torque and after cyclic loading.[De Mori, Renato] Sao Leopoldo Mand Coll, Dept Prosthesis, Vitoria, Brazil[Ribeiro, Cyntia Ferreira; da Silva-Concilio, Lais Regiane; Claro Neves, Ana Christina] Universidade de Taubaté (Unitau), Dept Prosthodont, Sao Paulo, Brazi

Effect of restorative material on mechanical response of provisional endocrowns: A 3D—FEA study

The goal of this study was to evaluate the stress distribution in an endocrown restoration according to different provisional restorative materials. An endodontically treated maxillary molar model was selected for conducting the finite element analysis (FEA), with a determined amount of dental remnant of 1.5 mm. The model was imported to the analysis software (ANSYS 19.2, ANSYS Inc., Houston, TX, USA) in STEP format. All contacts were considered perfectly bonded. The mechanical properties of each structure were considered isotropic, linear, elastic, and homogeneous. Three different provisional restorative materials were simulated (acrylic resin, bis-acrylic resin, and resin composite). An axial load (300 N) was applied at the occlusal surface in the center of the restoration. Results were determined by colorimetric stress maps of maximum principal stress, maximum shear stress, and total deformation. The different materials influenced the stress distribution for all structures; the higher the material’s elastic modulus, the lower the stress magnitude on the cement layer. In the present study, all provisional restorative materials showed similar stress patterns in the endocrown and on the cement layer however, with different magnitude. Based on this study limitation, the use of resin composite to manufacture provisional endocrowns is suggested as a promising material to reduce the stresses in the cement layer and in the dental tissue surfaces

Effect of polymerization method and fabrication method on occlusal vertical dimension and occlusal contacts of complete-arch prosthesis

Made available in DSpace on 2019-09-12T16:57:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2018PURPOSE. This study evaluated the dimensional stability of a complete-arch prosthesis processed by conventional method in water bath or microwave energy and polymerized by two different curing cycles. MATERIALS AND METHODS. Forty maxillary complete-arch prostheses were randomly divided into four groups (n = 10): MW1 - acrylic resin cured by one microwave cycle; MW2 - acrylic resin cured by two microwave cycles: WB1 - conventional acrylic resin polymerized using one curing cycle in a water bath; WB2 - conventional acrylic resin polymerized using two curing cycles in a water bath. For evaluation of dimensional stability, occlusal vertical dimension (OVD) and area of contact points were measured in two different measurement times: before and after the polymerization method. A digital caliper was used for OVD measurement. Occlusal contact registration strips were used between maxillary and mandibular dentures to measure the contact points. The images were measured using the software IpWin32, and the differences before and after the polymerization methods were calculated. The data were statistically analyzed using the one-way ANOVA and Tukey test (alpha=.05). RESULTS. The results demonstrated significant statistical differences for OVD between different measurement times for all groups. MW1 presented the highest OVD values, while WB2 had the lowest OVD values (P<.05). No statistical differences were found for area of contact points among the groups (P=.7150). CONCLUSION. The conventional acrylic resin polymerized using two curing cycles in a water bath led to less difference in OVD of complete-arch prosthesis.[Barbosa Lima, Ana Paula; Vitti, Rafael Pino; Amaral, Marina; Claro Neves, Ana Christina; da Silva Concilio, Lais Regiane] Universidade de Taubaté (Unitau), Dent Sch, Dept Prosthodon